How it works

When you choose a file, your browser reads it and processes it locally using JavaScript and WebAssembly, a technology that runs compiled code, such as the PDF engine, on your device. The result is created on your device and offered to you as a download. There is no server step in between, so your PDF is not uploaded.

Like any website, the server receives the standard technical data of a page request, such as your IP address and the page you asked for, so it can deliver the site. It does not receive your files or anything inside them.

1. Open your browser's developer tools (F12, or Ctrl+Shift+I on Windows and Linux, Cmd+Option+I on Mac).

2. Open the Network tab and clear the list of requests.

3. Use any tool on this site: select a file and run it.

4. Look at the requests that appear. You will see scripts and the PDF engine being downloaded, but no request that sends your file anywhere.

Because your own device does the work, very large PDFs can be slow or fail on phones and computers with little memory. PDFs that need a password to open can't be processed until you remove the password with the Unlock PDF tool, and only if you are allowed to open the document.